Peelably laminated containers made of synthetic resins are known and obtained by peelably laminating an outer layer that forms an outer shell of a finite shape and an inner layer that forms a deformable inner bag. These blow-molded bottles are generally referred to as delaminated bottles.
An outer parison and an inner parison having no compatibility with each other are first extruded together to give a laminated parison. This laminated parison is then blow-molded into the peelably laminated synthetic resin container. At that time, the bottom portion is pinched with the pinch-off of the blow mold and is pressed flat to form a bottom seal. Since the bottom seal has basically a laminated structure consisting of the outer layer and the inner layer, which are not compatible with each other, there was dissatisfaction in that the outer layer is easily cracked at the bottom.
As a conventional art to relieve this dissatisfaction, there is Japanese Laid-Open Patent Application No. 1996-216238. In the configuration of that invention, the bottom portion is pinched with the pinch-off of the blow mold and is pressed flat to form the bottom seal, as described above, but the seal is overlaid with a pair of ribs and pressed together so that a ridge is formed along the parting line. Some interlocks are provided at several points along the seal as both ribs bite into each other.
In this conventional art, the bottom seal is formed into a ridge having a certain height and width. As a result, the bottom seal has a large area of pressed contact between the outer layer and the inner layer. The interlocks provided at several points not only increase the area of pressed contact further, but also increase resistance to the shearing force that is parallel to the plane of pressed contact, thereby making it possible to obtain a bottom seal having a mechanical strength that is high enough to prevent the bottom seal from cracking.
However, in the above-described conventional art, there are cases of cracking in the bottom seal because of the effect of time-lapsed shrinkage at the bottom, which takes place after the containers have been blow-molded. The problem of bottom cracking is often found especially in large-size containers of this conventional art when they are dropped to the floor or when they experience a shock.
However, in the above-described conventional art, there are cases of cracking in the bottom seal because of the effect of time-lapsed shrinkage at the bottom, which takes place after the containers have been blow-molded. The problem of bottom cracking is often found especially in large-size containers of this conventional art when they are dropped to the floor or when they experience a shock.
Therefore, the blow-molded containers of this kind are required to go through complete cool-down and shrinkage within the mold. A problem arises here because the bottom seal has large height, thickness, and cubic volume, which need long hours of cooling and thus result in quite low efficiency in the production of containers.
Utility models laid open No. 1982-44063 and No. 1995-22951 describe conventional-art pouring vessels of the squeezable type, which comprise an inner container and an outer container in which to put the inner container.
The conventional art described in utility model laid open No. 1982-44063 refers to a pouring vessel comprising an inner container and an outer squeezable container having an air hole at the bottom. The content is discharged from the inner container by squeezing the outer container. Then, outside air is introduced into the void between the outer container and the inner container. At that time, the inner container maintains its deformed shape, while the outer container returns to the original shape because of its restoring force.
The conventional art described in utility model laid open No. 1995-22951 refers to another pouring vessel comprising an inner container and an outer squeezable container combined and fitted to each other. The inner container is provided with the first check valve that permits the content to pass through the valve and come out of the inner container but does not permit outside air to enter the inner container. The outer container is provided with the second check valve that permits outside air to enter the void between both containers, but does not permit air to escape from the void.
The method of utilizing a pair of adhered zones of the vertical strip type is also generally in use. These adhered zones adhere and fix the outer container and the inner container to each other over the entire height of the containers and restrict the deflationary deformation so as to keep the inner container at a certain shape that gives no shrinkage in the height direction, thereby ensuring the flow path for the content and making the discharge operation smooth. A simple and effective method is to dispose a pair of adhered zones at axisymmetric positions on the central axis of the body.
However, in order to make the adhered zones fulfill their function, it is necessary for these adhered zones to have a certain width. The adhered zones thus formed naturally have to be thick. On the other hand, the rest of the body of the outer container comprises a relatively thin wall so that the body gives flexibility to the squeezable container. Here is where problems arise. A problem is that the adhered zone forms a rib that prevents uniform squeezable deformation. Another problem is that the users feel strangeness in the touch with a hand. Still another problem is that the adhesive resin used to form the adhered zone is expensive.
The outer surface of the container body is usually an important portion of a commercial product from an outer-appearance point of view because a label is attached or printed on this surface to show the product name, and/or decoration is added. The formation of adhered zones causes irregularity on the outer surface of the body, and this irregularity is a process problem as well as the appearance problem. Furthermore, the rib-like adhered zones are conspicuous by themselves.
This invention has been made to solve these problems in the conventional art, owing to the configuration, such as the number and disposition, of the adhered zones of the vertical strip type used to adhere and fix the outer layer (the outer container) and the inner layer (the inner container).
Firstly, the technical problem of this invention is to achieve strong adhesion at the bottom seal between the outer layers and the inner layers, or between outer layers themselves by way of the inner layers, without increasing the bulk of the bottom seal. An object of this invention is to provide a peelably laminated, blow-molded synthetic resin container having high productivity and economical efficiency without a decrease in the bottom strength and the ability of the container to sit on the bottom.
Secondly, another technical problem of this invention is to form the adhered zones that minimize their adverse effect on the outer appearance and enable the outer container to be uniformly squeezed. Another object of this invention is to provide a blow-molded container of the squeezable type at a low cost, which is capable of achieving smooth discharge operation to the last moment and having highly aesthetic appearance.